A method for reducing dislocation threading using a suppression implant

ABSTRACT

The present invention provides a method for manufacturing a semiconductor device. In one embodiment, the method for manufacturing the semiconductor device includes a method for manufacturing a zener diode, including among others, forming a doped well within a substrate and forming a suppression implant within the substrate. The method for manufacturing the zener diode may further include forming a cathode and an anode within the substrate, wherein the suppression implant is located proximate the doped well and configured to reduce threading dislocations.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed, in general, to dislocation threadingand, more specifically, to a method for reducing dislocation threadingusing a suppression implant.

BACKGROUND OF THE INVENTION

In integrated circuit fabrication, dopants are frequently introducedinto semiconductor substrates to provide the semiconductor substratewith certain electrical characteristics. High-energy implants (e.g.,implants using an implant energy in excess of about 150 keV) are anincreasingly important method for introducing dopants into semiconductorsubstrates. At these high energies, the dopant profile is tailored toprovide the desired concentration of dopant within the desired distancefrom the surface of the semiconductor substrate.

It is well recognized, however, that such high-energy implants,particularly when used in combination with high dopant doses, may leadto certain long-term undesirable defects. For instance, it is wellrecognized that high-energy implants tend to form long dislocationdipoles (also referred to as threading dislocations) after a furnaceanneal of the implanted substrates. These dislocations are typicallygenerated in the substrate at the approximate depth of the meanprojected range of the implanted ions. Moreover, the dislocations tendto migrate to the substrate surface and have been found to cause highjunction leakage currents, Gate Oxide Integrity issues and otherelectrical problems.

It has been observed that the threading dislocation density caused byhigh energy Boron implants is much greater than other implant speciesand that the threading dislocations are generated under a variety ofdifferent anneal conditions (e.g., a post implant anneal conducted at900° C. for about 30 minutes). It has been observed that the threadingdislocation density has strong dose dependence, with a maximum defectdensity observed at Boron doses ranging from about 5E13 atoms/cm² toabout 2E14 atoms/cm², with a peak defect density at a Boron dose ofabout 1E14 atoms/cm².

The industry has attempted to address these threading dislocations in anumber of different ways. First, the industry attempted reducing orincreasing the Boron implant dose to a value outside of the range thatbrings about the aforementioned maximum defect density. This methodposes several difficulties or barriers to include requiring devices orcomponents to operate within a different doping profile (e.g. dopantwell) than intended or designed; this is especially true to High Voltagedevices and components where the well doping sets breakdowncharacteristics for the component. Second, the industry proposed atwo-step anneal wherein the substrate is first annealed at a lowertemperature for a longer time period and then annealed at the typicaltemperature. The two-step anneal reduced the density of threadingdislocations in Boron-implanted substrates, however, the 20 or so houranneal is simply too long to be practical in commercial processes forsemiconductor processing.

Consequently, processes that reduce the threading dislocations caused byhigh-energy implants and that are compatible with commercial processesfor device fabrication are sought.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, thepresent invention provides a method for manufacturing a zener diode anda method for manufacturing a semiconductor device. In one embodiment,the method for manufacturing the zener diode includes, among others,forming a p-type well within a substrate and forming a Fluorine implantwithin the substrate. The method for manufacturing the zener diode mayfurther include forming a cathode and an anode within the substrate,wherein the Fluorine implant is located proximate the p-type well andconfigured to reduce threading dislocations.

In an alternative embodiment, the method for manufacturing thesemiconductor device includes forming a doped well within a substrate,and forming a suppression implant within the substrate using an energyranging from about 120 KeV to about 540 KeV and a dose of at least about1.5E14 atoms/cm², wherein the suppression implant is located proximatethe doped well.

An alternative embodiment provides a zener diode. For instance, thezener diode may include a p-type well located within a substrate and aFluorine implant located within the substrate proximate the p-type welland configured to reduce threading dislocations. The zener diode in thisembodiment may further include a cathode and an anode located within thep-type well.

A semiconductor device is also provided by the present invention. Thesemiconductor device, without limitation, may include a doped welllocated within a substrate, one or more active junctions located withinthe doped well, and a suppression implant located within the doped well.In one embodiment, a peak concentration of the suppression implant islocated between a peak concentration of the p-type well and the one ormore active junctions.

The present invention further provides a voltage protection circuit. Thevoltage protection circuit may include: 1) an input pad, 2) one or morezener diodes electrically coupled to the input pad, the one or morezener diodes configured to clamp the input voltage, and 3) a circuit forreceiving the input voltage or the clamped input voltage. In oneembodiment, the one or more zener diodes are substantially similar tothose discussed in the paragraph directly above.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a sectional view of a semiconductor devicemanufactured in accordance with the principles of the present invention;

FIGS. 2 thru 7 illustrate sectional views showing how one might, in anembodiment, manufacture a semiconductor device in accordance with theprinciples of the present invention; and

FIG. 8 illustrates a combined block diagram/schematic diagram showing anembodiment of a protection circuit utilizing a zener diode as a clamp.

DETAILED DESCRIPTION

The present invention is based, at least in part, on the recognitionthat suppression implants may be used proximate doped wells,particularly p-type Boron doped wells, to reduce (e.g., suppress)threading dislocations that may form therein and cause leakage paths orother physical damage to the active device area. More specifically, thepresent invention has recognized that the placement of a suppressionimplant (e.g., a Fluorine implant in one embodiment) between the activejunctions in the doped well and a peak concentration of the doped welldopant, reduces or suppresses the aforementioned threading dislocations.The present invention has further recognized that the placement of thesuppression implant within about 1 micron from the peak concentration ofthe doped well dopant, and more specifically within about 0.5 micronsfrom the peak concentration of the doped well dopant, may providesuperior results.

Turning now to FIG. 1, illustrated is a sectional view of asemiconductor device 100 manufactured in accordance with the principlesof the present invention. The semiconductor device 100 initiallyincludes a substrate 110. Located within the substrate 110 in theembodiment of FIG. 1 is a doped well region 120. The doped well region120 may comprise various different dopants and configurations and remainwithin the purview of the present invention. However, in one particularembodiment, the doped well region 120 is a p-type doped well region, andmore specifically a Boron doped well region.

Located within the substrate 110 in the embodiment of FIG. 1 is animplant 130. The implant 130, which in one embodiment is an n-typedopant such as arsenic, is positioned within the doped well region 120.The implant 130, as opposed to the doped well region 120, is a veryshallow implant, for example extending on the order of about 0.4 micronsinto the substrate 110.

The semiconductor device 100 of FIG. 1, in accordance with the inventiveaspects of the present invention, includes a suppression implant 140 inthe substrate 110. In FIG. 1, the suppression implant 140 is locatedbetween a peak concentration of the doped well region 120 and activejunctions 150, 155, which will be discussed more fully below. In oneparticularly advantageous embodiment, the suppression implant 140 islocated within about 1 micron of the peak concentration of the dopedwell region 120. In another particularly advantageous embodiment, thesuppression implant 140 is located within about 0.5 microns of the peakconcentration of the doped well region 120. It has been observed thatpositioning the suppression implant 140 within about 1 micron providesenhanced threading dislocation reduction or suppression. It is believedthat reducing the 1 micron to about 0.5 microns or less provides evensuperior threading dislocation reduction or suppression.

The suppression implant 140, when manufactured consistent with theprinciples of the present invention, may comprise certain differentdopants. For example, in one embodiment the suppression implant 140comprises a group 17 element (e.g., I.U.P.A.C. convention standard) suchas Fluorine, the suppression implant 140 thus being a Fluorine implant.Such Fluorine suppression implants have been subjected to significanttesting, and have in turn been found to substantially reduce or suppressthe aforementioned threading dislocations.

Nevertheless, other group 17 elements might also be found to provide thesame advantageous results as the Fluorine implant. In addition to thegroup 17 elements, other separate embodiments might exist wherein thesuppression implant includes a group 14 element (e.g., Carbon implant,Silicon implant, etc.), a group 15 element (e.g., Nitrogen implant), ora group 18 element (e.g., Neon implant, Argon implant, etc.) Combinationsuppression implants, for example by combining any two or more of thepreviously listed elements, have not been tested, but might also work.

The semiconductor device 100 of FIG. 1 further includes one or moreactive junctions 150, 155 located within the substrate 110. In theembodiment shown, the active junctions 150 are anodes and the activejunction 155 is a cathode, as might be used in a zener diode. Thus, inthe embodiment of FIG. 1 the semiconductor device 100 is configured as azener diode. Other embodiments for the semiconductor device 100,however, also exist. For example, the semiconductor device 100 mightalso be a metal oxide semiconductor (MOS) device. In this embodiment theactive junctions 150, 155 would be configured as source/drain regions ofthe MOS device. Alternatively, the semiconductor device 100 might be abipolar transistor. In this embodiment the active junctions 150, 155,would be configured as at least one of a collector, base or emitter ofthe bipolar transistor.

Likewise, the semiconductor device 100 might be other p-n diodes, asopposed to strictly a zener diode.

The semiconductor device 100 of FIG. 1 experiences less threadingdislocations than a conventional semiconductor device not having thediscussed suppression implants. Because the semiconductor device 100 hasreduced or suppressed threading dislocations, the possibility forleakage paths is greatly reduced.

Turning now to FIGS. 2-7, illustrated are sectional views illustratinghow one might, in an advantageous embodiment, manufacture asemiconductor device similar to the semiconductor device 100 depicted inFIG. 1. FIG. 2 illustrates a sectional view of a partially completedsemiconductor device 200 manufactured in accordance with the principlesof the present invention. The semiconductor device 200 of FIG. 2includes a substrate 210. The substrate 210 may, in an exemplaryembodiment, be any layer located in the semiconductor device 200,including a wafer itself or a layer located above the wafer (e.g.,epitaxial layer). In the embodiment illustrated in FIG. 2, the substrate210 is a p-type substrate; however, one skilled in the art understandsthat the substrate 210 could be an n-type substrate without departingfrom the scope of the present invention. In such a case, each of thedopant types described throughout the remainder of this document mightor might not be reversed. For clarity, no further reference to thisopposite scheme will be discussed.

Located within the substrate 210 is a doped well region 240. The dopedwell region 240 may comprise various different dopants while remainingwithin the purview of the present invention. Nevertheless, in theembodiment of FIG. 2, the doped well region 240 is a p-type doped wellregion, and more specifically a Boron doped well region.

The doped well region 240 may be formed using conventional or otherprocesses. Accordingly, a conventionally patterned photoresist layer 220and implant dose 230 could be used to form and define the doped wellregion 240. For example, using the photoresist layer 220 and implantdose 230, the doped well region 240 could be implanted with a Borondopant dose ranging from about 5E13 atoms/cm² to about 2E14 atoms/cm².Such a Boron dose might be implanted using an energy ranging from about100 keV to about 500 keV, among others. This results in the doped wellregion 240 having a peak dopant concentration ranging from about 5E16atoms/cm³ to about 5E18 atoms/cm³. The peak dopant concentration, in theaforementioned embodiment, would likely be located from about 1.2microns to about 2.0 microns from the surface of the substrate 210.

The term peak concentration, as used herein, means the highest dopantconcentration of a particular dopant located within a doped region. Forinstance, in the Boron doped well region, the peak concentration wouldbe the highest Boron concentration located therein. In turn, thelocation of the peak concentration, as used herein, means the depth intothe substrate 210 that the highest dopant concentration is located.

Turning now to FIG. 3, illustrated is the semiconductor device 200 ofFIG. 2 after adding an additional implant 320 into the substrate 210.The additional implant 320 may also comprise many different dopantswhile staying within the purview of the present invention. Nevertheless,in the embodiment of FIG. 3, the additional implant 320 comprises ann-type arsenic implant.

In the illustrative embodiment of FIG. 3, the additional implant 320 isimplanted into the doped well region 230 using the previously formedphotoresist layer 220 and an implant dose 310. Because the samephotoresist layer 220 was used to form the doped well region 240 and theadditional implant 320, the additional implant 320 is located in thesame lateral position as the doped well region 240. Using thephotoresist layer 220, the additional implant 310 could be implantedwith an arsenic dopant dose ranging from about 5E14 atoms/cm² to about5E15 atoms/cm². Such an arsenic dose might be implanted using an energyranging from about 50 keV to about 200 keV, among others. This resultsin the additional implant 310 having a peak dopant concentration rangingfrom about 1E19 atoms/cm³ to about 1E21 atoms/cm³. Because theadditional implant 310 is implanted using a lesser energy than the dopedwell region 230, the additional implant 310 tends to be a much shallowerimplant.

Turning now to FIG. 4, illustrated is the semiconductor device 200 ofFIG. 3 after forming a suppression implant 420 within the substrate 210,and more particularly within the doped well region 240. The suppressionimplant 420 may comprise various different dopants. For instance, thesuppression implant 420, among others, may comprise different group 14,group 15, group 17 or group 18 elements. Depending on the particularembodiment being used, the suppression implant 420 could comprise aFluorine implant, Carbon implant, Silicon implant, Nitrogen implant,Neon implant, or Argon implant, without limitation. The embodiment ofFIG. 4, however, uses the Fluorine implant for the suppression implant420. It should also be noted that other embodiments may exist whereincombination suppression implants, for example by combining any two ormore of the previously listed elements, might also be used.

The location of the suppression implant 420 within the substrate 210 isparticularly important to the effectiveness thereof. In a general sense,the suppression implant 420 should be located within the doped wellregion 240. However, in certain embodiments the suppression implant 420is located between a peak concentration of the doped well region 240 andthe lowest portion of the active junctions 530, 630 (see FIGS. 5 and 6,discussed below). In other embodiments, the suppression implant 420 islocated within about 1 micron of the peak concentration of the dopedwell region 240. In even further embodiments, the suppression implant420 is located within about 0.5 microns of the peak concentration of thedoped well region 240.

In the illustrative embodiment of FIG. 4, the suppression implant 420 isimplanted into the doped well region 240 using the previously formedphotoresist layer 220 and an implant dose 410. Because the samephotoresist layer 220 was used to form the doped well region 240, theadditional implant 320, and the suppression implant 420, the suppressionimplant 420 is located in the same lateral position as the doped wellregion 240 and the additional implant 320. Using the photoresist layer220, the suppression implant 420 could be implanted, in one embodiment,with a Fluorine dopant dose of at least about 1.5E14 atoms/cm². In analternative embodiment, the Fluorine dopant dose might range from about1E13 atoms/cm² and up. Such Fluorine doses might be implanted using anenergy ranging from about 120 keV to about 540 keV. The disclosed energyvalues and doses are particularly adept at positioning the suppressionimplant 420 in the appropriate location. The resulting suppressionimplant 420 would likely have a peak dopant concentration ranging fromabout 1E17 atoms/cm³ to about 1E19 atoms/cm³.

Turning now to FIG. 5, illustrated is the semiconductor device 200 ofFIG. 4 after using a patterned photoresist layer 510 and implant dose520 to form active junctions 530 within the substrate 210. The activejunctions 530 illustrated in FIG. 5 happen to be anodes, as might beused in a zener diode. However, as previously mentioned, the activejunctions 530 could comprise different features and remain within thepurview of the present invention. Given that the active junctions 530are configured as anodes in the embodiment of FIG. 5, the activejunctions 530 might be doped with a p-type dopant, for example Boron.

The processes that might be used to form the active junctions 530 withinthe substrate 210 may be conventional. For example, using thephotoresist layer 510, the active junctions 530 could be implanted intothe substrate 210 using a dopant (e.g., Boron) dose ranging from about5E14 atoms/cm² to about 5E15 atoms/cm². Such a dose might be implantedusing an energy ranging from about 20 keV to about 110 keV. Thedisclosed energy values and doses are particularly able to position theactive junctions 530 in the appropriate location, which in oneembodiment is above the suppression implant 420. The resulting activejunctions 530 would likely have a peak dopant concentration ranging fromabout 1E19 atoms/cm³ to about 1E21 atoms/cm³.

Turning now to FIG. 6, illustrated is the semiconductor device 200 ofFIG. 5 after using a patterned photoresist layer 610 and implant dose620 to form an active junction 630 within the substrate 210. Given thatthe semiconductor device 200 of FIG. 6 is configured as a zener diode,the active junction 630 is a cathode. Again, as previously mentioned,the active junction 630 could comprise different features and remainwithin the purview of the present invention. Given that the activejunction 630 is configured as a cathode, the active junction 630 mightbe doped with an n-type dopant, for example arsenic or phosphorous.

The processes that might be used to form the active junction 630 withinthe substrate 210 may be conventional. For example, using thephotoresist layer 610, the active junction 630 could be implanted intothe substrate 210 using a dopant (e.g., arsenic or phosphorous) doseranging from about 5E14 atoms/cm² to about 5E15 atoms/cm². Such a dosemight be implanted using an energy ranging from about 20 keV to about100 keV. The disclosed energy values and doses are particularly able toposition the active junction 630 in the appropriate location, which inone embodiment is above the suppression implant 420. The resultingactive junction 630 would likely have a peak dopant concentrationranging from about 5E19 atoms/cm³ to about 5E21 atoms/cm³.

At this point in the manufacture of the semiconductor device 200, thedoped well region 240, the additional implant 320, the suppressionimplant 420, and the active junctions 530, 630, have likely beensubjected to various anneals (or diffusions). For example, thosefeatures (e.g., features 240, 320, 42, 530 and 630) might be subjectedto anneals using temperatures ranging from about 800° C. to about 1100°C. from seconds to hours to activate the features or set junction depthsto desired levels. The timing of the anneals is important to the presentinvention. For instance, while the anneals may be conducted at variousdifferent times, they should generally be conducted before formation ofthe wells or after implantation of the suppression implant 420, but notbetween the formation of the wells and the suppression implant 420.Generally, however, such anneals would be conducted at the end ofimplantation processes, such that only a single anneal may be requiredfor a given mask/implant step.

Turning lastly to FIG. 7, illustrated is the semiconductor device 200 ofFIG. 6 after forming isolation structures 710 in or over the substrate210 and contact features 720 for contacting the active junctions 530,630. Those skilled in the art appreciate the many different processesthat might be used to form the isolation structures 710 and contactfeatures 720. Accordingly, no further detail need be given for theirmanufacture. After completing the isolation structures 710 and contactfeatures 720, a device similar to the semiconductor device 100 of FIG. 1might result.

The process for manufacturing the semiconductor device 200 illustratedin FIGS. 2 thru 7 is but one embodiment of how a semiconductor devicemight be manufactured in accordance with the principles of the presentinvention. For example, the order of formation of the doped well region240, additional implant 320 and suppression implant 420, and for thatmatter even possibly the active junctions 530, 630, might be rearranged.Again, an importance is that the suppression implant 420 should beformed prior to performing any anneals directed at activating any of thepreviously formed features 240, 320, 530, 630.

Turning lastly to FIG. 8, illustrated is a combined blockdiagram/schematic diagram showing an embodiment of the invention, aninput ESD protection circuit 800 utilizing a zener diode 840 as a clamp.In the embodiment shown, the zener diode 840 is substantially similar tothe zener diode 100 illustrated in FIG. 1, as well as functions as asecondary clamp. Other embodiments of the zener diode 840, however, alsoexist.

In the embodiment of FIG. 8, an input pad 810 is connected to a primaryclamp 820 and a current limit 830. Current limit 830 is also connectedto the zener diode 840, which clamps the voltage to a level that issafe, thereby protecting the circuit 850 (particularly gate oxide orsource/drain junctions of MOS transistor devices that may be locatedwithin the circuit 850).

Those skilled in the art to which the invention relates will appreciatethat other and further additions, deletions, substitutions andmodifications may be made to the described embodiments without departingfrom the scope of the invention.

1. A method for manufacturing a zener diode, comprising: forming ap-type well within a substrate; forming a Fluorine implant within thesubstrate; and forming a cathode and an anode within the substrate,wherein the Fluorine implant is located proximate the p-type well andconfigured to reduce threading dislocations.
 2. The method as recited inclaim 1 wherein a peak concentration of the Fluorine implant is locatedwithin about 1 micron of a peak concentration of the p-type well.
 3. Themethod as recited in claim 1 wherein the forming the Fluorine implantincludes forming the Fluorine implant using an energy ranging from about120 KeV to about 540 KeV and a Fluorine dose of at least about 1.5E14atoms/cm².
 4. The method as recited in claim 1 wherein the p-type wellis a Boron doped well.
 5. A method for manufacturing a semiconductordevice, comprising: forming a doped well within a substrate; forming asuppression implant within the substrate using an energy ranging fromabout 120 KeV to about 540 KeV and a dose of at least about 1.5E14atoms/cm², wherein the suppression implant is located proximate thedoped well and configured to reduce threading dislocations.
 6. Themethod as recited in claim 5 wherein the suppression implant is aFluorine implant.
 7. The method as recited in claim 5 wherein thesuppression implant is a Carbon implant, a Silicon implant, a Nitrogenimplant, a Neon implant or an Argon implant.
 8. The method as recited inclaim 5 wherein a peak concentration of the suppression implant islocated within about 1 micron of a peak concentration of the doped well.9. The method as recited in claim 5 wherein the doped well is a Borondoped well.
 10. A zener diode, comprising: a p-type well located withina substrate; a Fluorine implant located within the substrate proximatethe p-type well and configured to reduce threading dislocations; and acathode and an anode located within the p-type well.
 11. The zener diodeas recited in claim 10 wherein a peak concentration of the Fluorineimplant is located between a peak concentration of the p-type well and alowest portion of the cathode and the anode.
 12. The zener diode asrecited in claim 10 wherein a peak concentration of the Fluorine implantis located within about 1 micron of a peak concentration of the p-typewell.
 13. The zener diode as recited in claim 10 wherein the p-type wellis a Boron doped well.
 14. A semiconductor device, comprising: a dopedwell located within a substrate; one or more active junctions locatedwithin the doped well; and a suppression implant located within thedoped well, wherein a peak concentration of the suppression implant islocated between a peak concentration of the p-type well and a lowestportion of the one or more active junctions.
 15. The semiconductordevice as recited in claim 14 wherein the suppression implant is aFluorine implant.
 16. The semiconductor device as recited in claim 14wherein the suppression implant is a Carbon implant, a Silicon implant,a Nitrogen implant, a Neon implant or an Argon implant.
 17. Thesemiconductor device as recited in claim 14 wherein a peak concentrationof the suppression implant is located within about 1 micron of a peakconcentration of the doped well.
 18. The semiconductor device as recitedin claim 14 wherein the one or more active junctions are at least one ofa collector, a base or an emitter of a bipolar transistor.
 19. Thesemiconductor device as recited in claim 14 wherein the one or moreactive junctions are source/drain regions of a metal oxide semiconductor(MOS) device.
 20. A voltage protection circuit, comprising: an inputpad; one or more zener diodes electrically coupled to the input pad, theone or more zener diodes configured to clamp the input voltage, each ofthe one or more zener diodes comprising: a p-type well located within asubstrate; a cathode and an anode located within the p-type well; and asuppression implant located within the substrate proximate the p-typewell and configured to reduce threading dislocations; and a circuit forreceiving the input voltage or the clamped input voltage.